Back in the day, kids got enemas for just about any malady such as a cold, tummy ache, headache, fever, or for just being lethargic or unruly. In some cases, kids got enemas because it was a particular day of the week. Most every home had an enema bag, sometimes visibly displayed, and sometimes hidden in a drawer or linen closet. Enemas were an accepted method of mitigating many different concerns and issues.
Our parents got enemas as well. They seldom checked into a hospital for an operation or procedure, without getting an enema as part of routine admission procedures. What was good for the goose, was good for the gander, and all of us ducklings as well.
It just happens that some of us developed an extraordinary affection for the magical virtues of a good enema. As far as "feeling the flow", that's just a part of the process. The answer to the question likely resulted in mom, or a nurse, raising or lowering the bag depending on the response. If I'm going solo, it's just a silent and rhetorical aspect of my psyche. Of course I can feel it, and the sensations are wonderful. If I'm not feeling it, well I guess I just need to make some adjustments in order to enjoy those sensations.
Maybe it is an age thing to some extent. We old farts have some wonderful memories and recollections, even if the enema was uncomfortable or given to address some type of negative behavior. When I was 20 something, enemas filled a void when my GF wasn't up to "getting it on".